Light-emitting apparatus, surface light source, and method for manufacturing package for light-emitting apparatus

ABSTRACT

A light-emitting apparatus of the present invention has (i) a semiconductor device which emits light toward a higher position than a substrate and (ii) a plurality of external connection terminals, and includes: a light-reflecting layer, provided on the substrate, which reflects the light emitted by the semiconductor device; and a covering layer which covers at least the light-reflecting layer and which transmits the light reflected by the light-reflecting layer. Further, the semiconductor device is provided on the covering layer, and is electrically connected to the external connection terminals via connecting portions, and the semiconductor device and the connecting portions are sealed with a sealing resin so as to be covered. Therefore, the light-emitting apparatus has increased efficiency with which light is taken out, and can prevent a reflecting layer from being altered, deteriorating, and decreasing in reflectance.

This Nonprovisional application claims priority under 35 U.S.C. §119(a)on Patent Application No. 2008-164910 filed in Japan on Jun. 24, 2008and Patent Application No. 2008-269858 filed in Japan on Oct. 20, 2008,the entire contents of which are hereby incorporated by reference.

TECHNICAL FIELD

The present invention relates light-emitting apparatuses each includinga light-emitting diode (LED) chip and a reflecting layer for efficientlytaking out light emitted by the LED. In particular, the presentinvention relates to a light-emitting apparatus that prevents thereflecting layer from being altered, deteriorating, and decreasing inreflectance.

BACKGROUND ART

FIG. 11 is a cross-sectional view illustrating a conventionallight-emitting apparatus in which an LTCC (low temperature co-firedceramic) substrate is used (see Patent Literature 1). The light-emittingapparatus includes an LTCC substrate 50, silver epoxy 52, reflectingbarriers 51, transparent epoxy 53, and LED dies 54. In this conventionalexample, light emitted by an LED die 54 is reflected by a reflectingbarrier 51, whereby a reduction in loss of the emitted light isachieved. Further, heat from the LED die 54 is dissipated by thereflecting barrier 51 into a related thermal diffusion section (notshown) and the LTCC substrate 50. LTCC packaging of a light-emittingapparatus in which an LTCC substrate is used is suitable in particularto diffusing heat generated by closely-packed LED dies or LED arrays.

FIG. 12 is a cross-sectional view illustrating an LTCC chip carrierhaving wire bonding (see Patent Literature 2). This LTCC chip carrierhas a heat spreader 67, a second LTCC layer 61, and a top LTCC layer 60stacked in this order on a motherboard 65. The top LTCC layer 60 has acavity in the center thereof. In the cavity, a single LED chip 4 isfixed with an adhesive or the like on a thermal via 62 formed so as topass through the second LTCC layer 61. The LED chip 4 is connected bywire bonding via a wire 90 to a second layer terminal 64 formed on thesecond LTCC layer 61. The second layer terminal 64 is connected via avia 68 to a top terminal 63 formed on the top LTCC layer 60.Furthermore, the top terminal 63 is connected by wire bonding via a wire91 to an external terminal 66 formed on the motherboard 65. The topterminal 63, the second layer terminal 64, the external terminal 66, andthe heat spreader 67 are made of conductors that can be co-fired. Thecavity inside the top LTCC layer 60 that contains the LED chip is sealedwith epoxy resin 69 or another type of organic material. Furthermore,for a thermal runaway, a heat sink 70 is placed below the motherboard 65by a variety of methods.

LTCC intrinsically has higher thermal conductivity than organicmaterial. Further, the provision of the thermal via 62 and a metalizedconductor surface causes a further increase in thermal conductivity,thus enabling an improvement in heat radiation properties of thelight-emitting apparatus.

Further, as a technique for improving the luminous efficiency of an LED,a technique of providing a metal reflecting layer between alight-emitting layer of the LED and a supporting substrate has beenproposed (Non Patent Literature 1). This means that the reflection bythe metal reflecting layer of light radiated from the LED toward thesupporting substrate enables an increase in the amount of light that isemitted by the LED.

CITATION LIST Patent Literature 1

-   Japanese Translation of PCT International Publication, Tokuhyo, No.    2007-533082 A (Publication Date: Nov. 15, 2007)

Patent Literature 2

-   Japanese Patent Application Publication, Tokukai, No. 2007-129191 A    (Publication Date: May 24, 2007)

Non Patent Literature 1

-   HITACHI Cable (Hitachi Cable, Ltd.), “Hitachi Cable has developed a    high-luminosity red LED chip 65 lumens/watt”, News Release:    Products, [online], Dec. 17, 2007, Hitachi Cable, Ltd., [retrieved    on May 1, 2008] Internet    (http://www.hitachi-cable.co.jp/products/news/20071217.html)

SUMMARY OF INVENTION Technical Problem

However, the conventional arrangements cause the following problems.

An LTCC substrate is a substrate made of a composite of ceramic andglass. Depending on the material, the LTCC substrate transmits orabsorbs light emitted by an LED chip, thereby causing a decrease inemission output. However, the conventional arrangements of PatentLiteratures 1 and 2 take no measures against light reflection or lighttransmission on a surface of an LTCC substrate. Further, since theconventional arrangements are each structured to have a step beside asurface on which an LED chip is mounted, thus causing a loss in emittedlight. Therefore, the conventional arrangements are not arranged torealize a high-power LED.

Further, in the arrangement of Non Patent Literature 1, unfortunately,the metal reflecting layer is altered or deteriorates, for example, dueto external moisture or oxygen and further decreases in reflectance dueto the alteration or deterioration.

The present invention has been made in view of the foregoing problems,and it is an object of the present invention to provide a light-emittingapparatus that has increased efficiency with which light is taken outand that prevents a reflecting layer from being altered, deteriorating,and decreasing in reflectance.

Solution to Problem

A light-emitting apparatus according to the present invention has (i) atlease one semiconductor device which emits light toward a higherposition than a substrate and (ii) a plurality of external connectionterminals, and includes: a light-reflecting layer, provided on thesubstrate, which reflects the light emitted by the at lease onesemiconductor device; and a covering layer which covers at least thelight-reflecting layer and which transmits the light reflected by thelight-reflecting layer. The at least one semiconductor device isprovided on the covering layer, and is electrically connected to theexternal connection terminals via connecting portions, and the at leastone semiconductor device and the connecting portions are sealed with asealing resin so as to be covered.

According to the foregoing arrangement, the light-reflecting layerreflects light emitted by the semiconductor device toward a lowerposition (toward the substrate), thereby enabling effective use of theemitted light with a reduction in loss of the emitted light. This makesit possible to increase the amount of light that is emitted by thelight-emitting apparatus. Further, since the light-reflecting layer iscovered with the covering layer, the light-emitting apparatus inhibitsthe light-reflecting layer from being altered or deteriorating.Furthermore, the light-emitting apparatus inhibits a decrease inreflectance from being caused by the alteration or deterioration.

A light-emitting apparatus according to the present invention includes:a light-emitting diode chip; a package, including a chip-mountingportion and a silver reflecting layer which reflects light emitted bythe light-emitting diode chip, in which the light-emitting diode chip isdie-bonded to the chip-mounting portion; and a sealing resin whichcovers the light-emitting diode chip, the silver reflecting layer beingcovered with a glass layer.

A method according the present invention for manufacturing a package fora light-emitting apparatus includes the steps of: preparing a pluralityof green sheets made mainly of alumina; performing a process of makingholes in the plurality of green sheets; filling the holes of theplurality of green sheets with at least either metal paste or glasspaste; and stacking and firing the plurality of green sheets so that themetal paste is covered with the glass paste, the steps being executed inthe order presented.

Advantageous Effects of Invention

In the light-emitting apparatus according to the present invention, thelight-reflecting layer reflects light emitted by the semiconductordevice toward a lower position (toward the substrate), thereby enablingeffective use of the emitted light with a reduction in loss of theemitted light. This makes it possible to increase the amount of lightthat is emitted by the light-emitting apparatus. Further, since thelight-reflecting layer is covered with the covering layer, thelight-emitting apparatus inhibits the light-reflecting layer from beingaltered or deteriorating. Furthermore, the light-emitting apparatusinhibits a decrease in reflectance from being caused by the alterationor deterioration.

Further, the light-emitting apparatus according to the present inventionsufficiently protects the light-reflecting layer by the covering layer,thus making it possible to apply dimethyl silicone or methyl rubber asthe sealing resin. Dimethyl silicone and methyl rubber are somewhatlower in gas sealing properties in some cases, but exhibit high heatresistance and a high degree of adhesion to glass.

In the method according to the present invention for manufacturing apackage for a light-emitting apparatus, at the same time as a substratematerial obtained by stacking green sheets is fired, a reflecting layerand a covering layer covering the reflecting layer are fired, whereby apackage for a light-emitting apparatus is manufactured. This makes itunnecessary to execute more than one firing step, thus achieving a lowcost.

For a fuller understanding of the nature and advantages of theinvention, reference should be made to the ensuing detailed descriptiontaken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a plan view schematically illustrating a light-emittingapparatus according to one embodiment of the present invention.

FIG. 2 is a plan view schematically illustrating wiring patterns of alight-emitting section of the light-emitting apparatus.

FIGS. 3( a) through 3(d) are cross-sectional views schematicallyillustrating steps of manufacturing the light-emitting apparatus.

FIG. 4 is a cross-sectional view schematically illustrating thelight-emitting apparatus.

FIG. 5 is a perspective view illustrating an LED light fixture, shapedinto a fluorescent light, in which the light-emitting apparatus is used.

FIG. 6 is a perspective view illustrating an LED light fixture, shapedinto a light bulb, in which the light-emitting apparatus is used.

FIG. 7( a) is a cross-sectional view schematically illustrating alight-emitting apparatus according to another embodiment of the presentinvention.

FIG. 7( b) is a plan view schematically illustrating the light-emittingapparatus.

FIG. 8 is a cross-sectional view schematically illustrating alight-emitting apparatus according to still another embodiment of thepresent invention.

FIG. 9 is a cross-sectional view schematically illustrating alight-emitting apparatus according to still another embodiment of thepresent invention.

FIG. 10 is a cross-sectional view schematically illustrating alight-emitting apparatus according to still another embodiment of thepresent invention.

FIG. 11 is a cross-sectional view schematically illustrating aconventional light-emitting apparatus.

FIG. 12 is a cross-sectional view schematically illustrating aconventional light-emitting apparatus.

FIG. 13 (a) is a plan view schematically illustrating a structure of alight-emitting apparatus according to still another embodiment of thepresent invention.

FIG. 13( b) is a cross-sectional view schematically illustrating thelight-emitting apparatus.

FIG. 14 is a flow chart illustrating a method for manufacturing alight-emitting apparatus.

FIGS. 15( a) through 15(d) are cross-sectional views illustrating how astack is arranged.

FIGS. 16( a) through 16(d) are cross-sectional views illustrating amethod for manufacturing the light-emitting apparatus.

FIG. 17 is a cross-sectional view schematically illustrating a structureof a light-emitting apparatus according to still another embodiment ofthe present invention.

FIG. 18 is a cross-sectional view schematically illustrating a structureof a light-emitting apparatus according to still another embodiment ofthe present invention.

FIG. 19( a) is a pattern diagram illustrating a structure of a surfacelight source according to still another embodiment of the presentinvention.

FIG. 19( b) is a cross-sectional view taken along the line A-A′ of FIG.19( a).

DESCRIPTION OF EMBODIMENTS Embodiment 1

FIG. 1 shows an overhead pattern diagram of a light-emitting apparatus1000 according to one embodiment of the present invention. Thelight-emitting apparatus 1000 includes a low temperature co-firedceramic (LTCC) substrate 1. On the low temperature co-fired ceramic(LTCC) substrate 1, a silver reflecting layer (not illustrated) and aglass layer (covering layer) 3 are formed in this order. Thelight-emitting apparatus 1000 has a light-emitting section 1001 providedon the glass later 3. The light-emitting section 1001 is sealed with aluminescent material-containing sealing resin 6. Further provided on theLTCC substrate 1 are a positive electrode external connection terminal 8and a negative electrode external connection terminal 7. Each of theexternal connection terminals has an external wire 15 connected thereto.The external wire 15 is run outward through an external wiring hole 16provided in the LTCC substrate 1. The LTCC substrate 1 has attachingportions 13 via which the light-emitting apparatus 1000 is screwed toanother apparatus. It should be noted here that the outer shape of thelight-emitting apparatus 1000 is substantially square and the shape ofthe light-emitting section 1001 is substantially rectangular.

FIG. 2 is a plan view illustrating wiring patterns or the like of thelight-emitting apparatus 1000. On the glass layer 3 formed on the LTCCsubstrate 1, a plurality of elongated rectangular wiring patterns(connecting portions) 9 are formed in parallel with one another and atdistances from one another. The wiring patterns 9 are connected to thepositive electrode external connection terminal 8 and the negativeelectrode external connection terminal 7. Provided between one wiringpattern 9 and another is a chip-mounting portion 41 on which an LED chip(semiconductor device) is mounted.

FIGS. 3( a) through 3(d) and FIG. 4 are cross-sectional viewsschematically illustrating a method for manufacturing a light-emittingapparatus 1000.

FIG. 3( a): On an LTCC substrate 1 having a thickness of 2 mm, a silverfilm is formed by plating, whereby a silver reflecting layer(light-reflecting layer) 2 having a thickness of 0.2 mm is formed.

On the silver reflecting layer 2, a glass layer 3 having a thickness of0.006 mm is formed.

On the glass layer 3, wiring patterns 9 (thickness 0.07 mm, width 0.45mm, interval 2 mm) are formed by screen printing. The method used hereis a method to impart wettability to a surface of the glass layer bycleaning the surface without roughening it, to provide the surface withspecial treatment that strengthens a chemical bond, to make the surfacecatalytically active, and to then plate the surface directly withelectroless nickel adjusted for glass material.

It should be noted here that the LTCC substrate 1 is made of a mixtureof borosilicate glass (Na₂O—B₂O₃—SiO₂) and SiO₂. The silver reflectinglayer 2 is made of silver or a silver alloy (Ag, AgPt, Ag—Bi, Ag—Ndbased alloy) composed mainly of silver. The glass layer 3 is made oftransparent borosilicate glass (Na₂O—B₂O₃—SiO₂) with use of a doctorblade method. The doctor blade method is one of the methods for formingceramic into sheets. This molding method regulates a space between anedge of a knife (doctor blade) and a carrier (carrier film, endlessbelt), and precisely controls the thickness of a slip (slurried slip orgel obtained by dispersing raw powder in a solvent) conveyed on thecarrier. Refer to:http://www.oit.ac.jp/www-ee/server/aplab/res/slurry.html).

FIG. 3( b): Between one wiring pattern 9 and another on the glasssubstrate 3, LED chips 4 (shorter-side width 0.24 mm, longer-side width0.48 mm, thickness 0.14 mm, quantity 36) are fixed with use of siliconeresin. Next, the LED chips 4 and the wiring patterns 9 are electricallyconnected with use of bonding wires (connecting portions) W. It shouldbe noted that each of the LED chips 4 includes an arrangement of acommonly-used LED chip.

FIG. 3( c): A substantially rectangular silicone rubber sheet 5 isdisposed onto the glass layer 3 so as to surround a region in which theLED chips have been placed. The silicone rubber sheet 5 is attachedfirmly onto the glass layer 3.

FIG. 3( d): Next, a sealing resin (silicone) 6 containing a luminescentmaterial (Eu:BOSE ((Ba.Sr)₂SiO₄:Eu)) is injected into an inner sidesurrounded by the silicone rubber sheet 5, and the sealing resincontaining the luminescent material is cured by heat.

Here, after a mixture of a luminescent substance and silicone resin thatis a transparent resin is injected into the frame constructed by thesilicone rubber sheet 5, the resin is cured over 30 minutes at 150° C.,with the result that a sealing resin 6 containing a luminescent materialis formed. After that, the silicone rubber sheet 5 is removed.

FIG. 4 is a cross-sectional view illustrating a light-emitting section1001 thus formed on the LTCC substrate 1.

The sealing resin 6 containing the luminescent material is formed so asto give off light corresponding to the point (x,y)=(0.345,0.35) on theCIE chromaticity diagram. Thus, the light-emitting section 1001 ismanufactured.

Such an arrangement as above allows light emitted by the LED chips 4 or,in particular, light from the lower surfaces of the LED chips 4 (towardthe substrate) to be reflected by the silver reflecting layer 2sandwiched between the LTCC substrate 1 and the glass substrate 3, thuslosslessly making effective use of the light emitted by the LED chips 4.This makes it possible to increase the amount of light that is emittedby the light-emitting apparatus 1000. Further, the silver reflectinglayer 2 both functions as a light-reflecting layer and functions todiffuse, in a direction along a surface of the package (i.e., in adirection parallel to the LTCC substrate 1), heat generated by the LEDchips 4. Further, since the LTCC substrate 1 has high heat conductivityand good heat radiation properties, the LED chips 4 can be integrated.This makes it possible to inhibit the light-emitting apparatus frombeing deformed due to heat, thus enabling suppression of a color shiftor the like.

Further, in the present embodiment, the silver reflecting layer 2 iscovered with the glass layer 3; therefore, the glass layer 3 can inhibitthe reflecting layer from being altered, deteriorating, and decreasingin reflectance. The glass layer 3 is more highly isolating againstoxygen, moisture, or the like than a common resin is. Therefore, theglass layer 3 can suppress a change over time in the silver reflectinglayer 2. Further, since the LTCC substrate 1 and the glass layer 3 bothcontain glass, the LTCC substrate and the glass layer exhibitsatisfactory adhesion to each other, thus further enhancing the effectof isolating the silver reflecting layer 2 from oxygen, moisture, or thelike.

The reflecting layer can be made of any metal or nonmetallic materialthat reflects light emitted by the LED chips, as well as theaforementioned silver or silver alloy. For example, when the reflectinglayer is made of a given metal or nonmetallic material having an opticalreflectance of not less than 90%, light emitted toward the LTCCsubstrate 1 can be efficiently used, so that the amount of light that isemitted by the light-emitting section 1001 can be increased.

Further, it is preferable that the wiring patterns 9 be made of amaterial containing gold, which is chemically stable. Furthermore, thepresent embodiment has a nickel layer formed between the wiring patterns9 and the glass layer 3, thus improving adhesion between the wiringpatterns 9 made of gold and the glass layer 3. This makes it possible tofurther inhibit a change over time from being caused by deterioration orthe like in the wiring patterns 9. Alternatively, instead of the nickellayer, a chrome layer may be formed.

It should be noted here that it is preferable that the glass layer 3 andthe LTCC substrate 1 be made of glass powder of borosilicate glass ofthe composition Na₂O—B₂O₃—SiO₂, because the borosilicate glass is low incoefficient of thermal expansion, high in thermal shock temperature, andhighly chemically resistant because of its high content of boron oxide.

The silicone rubber sheet 5 (see FIG. 3( d)) functions as a dam (to stopthe resin from leaking) in applying the transparent resin containing theluminescent material. As such, the silicone rubber sheet 5 ischaracterized in such a way as to be called a dam sheet. Further, thedam sheet can be used a number of times. Further, the dam sheet ischaracterized in that changes in shape of the dam sheet easily allowvariations in shape of the light-emitting section 1001 (i.e., shape ofthe luminescent material-containing sealing resin 6).

The glass layer 3 and the silver reflecting layer 2 are formed acrossthe whole surface, surrounded by the silicone rubber sheet 5, on whichthe LED chips 4 have been mounted.

It should be noted here that since such an arrangement of the region inwhich the LED chips 4 are mounted makes it possible to freely determinethe pitches at which the LED chips are placed along a direction parallelto the wiring patterns 9, it is possible to easily adjust the luminanceof the light-emitting apparatus, adjust the chromaticity of thelight-emitting apparatus, and take measures against heat generated bythe light-emitting apparatus.

As applied examples of a light fixture made with use of a light-emittingapparatus 1000, FIG. 5 shows a pattern diagram of an LED lamp 7000shaped into a fluorescent light, and FIG. 6 shows a pattern diagram ofan LED lamp 9000 shaped into a light bulb. The LED lamp 9000 has athread 14. The LED lamp 7000 and the LED lamp 9000 are arranged in thesame manner as a common LED lamp shaped into a fluorescent light and acommon LED lamp shaped into a light bulb, respectively, except that theyeach include a light-emitting apparatus 1000.

Embodiment 2

FIG. 7( a) is a cross-sectional view schematically illustrating alight-emitting apparatus 1002 according to another embodiment of thepresent invention, and FIG. 7( b) is a plan view illustrating thelight-emitting apparatus 1002. For convenience of explanation, membershaving the same functions as those used in Embodiment 1 are given thesame reference numerals, and will not be described below. Thelight-emitting apparatus 1002 includes: a low temperature co-firedceramic (LTCC) substrate 10; a silver reflecting layer 2 formed on theLTCC substrate 10; a glass layer 3 covering the silver reflecting layer2; LED chips 4 placed on the glass layer 3; and positive and negativeelectrode external connection terminals 81 and 71 formed on the glasslayer 3. The LED chips 4 are electrically connected to each of theexternal connection terminals 81 and 71 via bonding wires W. The LEDchips 4 and the bonding wires W are sealed with a domed luminescentmaterial-containing sealing resin 61. The external connection terminals81 and 71 are formed so as to extend to opposite side surfaces of theLTCC substrate 10.

The LTCC substrate 10 includes multiple (ten) LTCC layers 10 a to 10 j,and a plurality of heat-radiating vias 21 made of silver are each formedso as to pass through the layers of the LTCC substrate 10, i.e., so asto extend in a direction perpendicular to the LTCC substrate 10, and areeach connected to the silver reflecting layer 2. It should be noted herethat the LTCC substrate 10 is made by stacking ten green sheets. Thepresent embodiment has four LED chips 4 placed therein. However, forsimplicity, FIG. 7( a) shows a cross-section of a single LED chip.

The following shows a method for manufacturing a light-emittingapparatus 1002.

Step (1): Raw material is prepared by blending/mixing ceramic powder(Al₂O₃ powder, 30 wt %) and glass powder (borosilicate glass powder, 70wt %) with a given ratio. To the raw material thus mixed, an organicbinder (acrylic resin) and a solvent (toluene) are added, and thendispersed uniformly. Thus made is material, called slurry, which servesas a basis for a green sheet. The slurry is applied onto a PET film by adoctor blade molding machine so as to have a given thickness, and thenreeled off after a drying step. A sheet-like material thus made iscalled a green sheet (thickness of 0.1 mm). The green sheet is cut tothe proper size, and then subjected to a process (punching process) ofmaking holes that are to serve as heat-radiating vias 21. The holes arefilled with heat-radiating material (silver paste). Thus made is asingle LTCC layer (thickness 0.1 mm). Ten LTCC layers (10 a, 10 b, 10 c,10 d, 10 e, 10 f, 10 g, 10 h, 10 i, 10 j) thus made are stacked,pressure-bonded by heat, and then subjected to a firing step (850° C.).Thus made is an LTCC substrate 10.

Step (2): On the LTCC substrate 10 (thickness 1 mm), a silver film(thickness 0.25 mm) is formed by plating, whereby a silver reflectinglayer 2 is formed. It should be noted here that the green sheet is madeof glass powder of borosilicate glass (Na₂O—B₂O₃—SiO₂) and ceramicpowder of Al₂O₃.

Step (3): On the silver reflecting layer 2, a glass layer 3 (thickness0.01 mm) is formed. It should be noted here that the glass layer 3 ismade of transparent borosilicate glass (Na₂O—B₂O₃—SiO₂) with use of adoctor blade method.

Step (4): On the glass layer 3, external connection terminals 71 and 81(thickness 0.7 mm, width 0.45 mm) are formed with gold by screenprinting.

Step (5): On the glass layer 3, LED chips 4 (shorter-side width 0.24 mm,longer-side width 0.48 mm, thickness 0.14 mm, quantity 4) are fixed withuse of silicone resin (not illustrated). Next, the LED chips 4 and theexternal connection terminals 71 and 81 are electrically connected withuse of bonding wires W.

Step (6): Next, a sealing resin (silicone) 61 containing a luminescentmaterial (Eu:BOSE) is formed, and the luminescent material-containingsealing resin 61 is cured by heat. The luminescent material-containingsealing resin 61 is formed by keeping a mixture of a luminescentmaterial and silicone resin that is a transparent resin at 150° C. over30 minutes and curing the resin. It should be noted that, in the presentembodiment, the luminescent material-containing sealing resin 61 isformed so as to give off light corresponding to the point(x,y)=(0.345,0.35) on the CIE chromaticity diagram. Thus, thelight-emitting section is manufactured.

It should be noted here that the silver reflecting layer 2 is effectivein taking out light emitted by the LED chips 4 toward the LTCC substrate10. Further, in the present embodiment, the silver reflecting layer 2 iscovered with the glass layer 3. This makes it possible to inhibit thereflecting layer from being altered, deteriorating, and decreasing inreflectance. The glass layer 3 is more highly isolating against oxygen,moisture, or the like than a common resin is, and therefore can suppressa change over time in the silver reflecting layer 2.

Further, the heat-radiating vias 21, made of silver, can effectivelyradiate heat outward so that heat generated by the LED chips 4 istransferred in a direction perpendicular to the substrate. This effectis more remarkable because the contact between the silver reflectinglayer 2 and the heat-radiating vias 21 allows the heat generated by theLED chips 4 to be efficiently transferred to the heat-radiating vias 21via the silver reflecting layer 2. The heat-radiating vias 21 can bemade of any metal, as well as silver. Alternatively, as with the silverreflecting layer 2, the heat-radiating vias 21 may be made of a silveralloy (AgPt, Ag—Bi, Ag—Nd based alloy) composed mainly of silver.

Further, it is possible to place a heat sink (not illustrated) on theunderside of the LTCC substrate 10 of the light-emitting apparatus 1002.Such a heat sink further increases the heat radiation properties of thelight-emitting apparatus, thus inhibiting a color shift from beingcaused by generated heat. In such a case, it is preferable that theheat-radiating vias 21 be in contact with the heat sink.

It should be noted the heat-radiating vias 21 have an effect ofreflecting light transmitted from the LED chip 4 into the LTCC substrate10. When the heat-radiating vias 21 are disposed so as to extend to aregion where the silver reflecting layer 2 is not formed as seen from asurface of the LTCC substrate 10, it is possible to better take outlight toward the surface of the LTCC substrate 10.

Embodiment 3

FIG. 8 is a cross-sectional view schematically illustrating alight-emitting apparatus 1005 according to another embodiment of thepresent invention. For convenience of explanation, members having thesame functions as those used in Embodiment 2 are given the samereference numerals, and will not be described below. The presentembodiment differs from Embodiment 2 in that the LED chips 4 and thebonding wires W are sealed with a domed sealing resin including aluminescent material-containing resin section 63 containing aluminescent material and a transparent resin section 64 formed so as tocover the luminescent material-containing resin section 63, instead ofbeing sealed with the luminescent material-containing resin. Theluminescent material-containing resin section 63 and the transparentresin section 64 are each domed.

Such an arrangement as above makes it possible to protect theluminescent material-containing resin section 63 by the transparentresin section 64. Further, since the sealing resin and each resinsection are domed, there are continuous changes in direction in whichirradiating light from the LED chip 4 is refracted. This makes itpossible to reduce spatial unevenness in intensity of the irradiatinglight.

The transparent resin section 64 is preferably made of raw materialcapable of securing transparency and high in hardness, but is notparticularly limited in material.

Embodiment 4

FIG. 9 is a cross-sectional view schematically illustrating alight-emitting apparatus 1003 according to another embodiment of thepresent invention. For convenience of explanation, members having thesame functions as those used in Embodiment 2 are given the samereference numerals, and will not be described below. The light-emittingapparatus 1003 includes: a low temperature co-fired ceramic (LTCC)substrate 11; a silver reflecting layer 2 formed on the LTCC substrate11; a glass layer 3 covering only the silver reflecting layer 2 on theLTCC substrate 11; LED chips 4 placed on the glass layer 3; and positiveand negative electrode external connection terminals 81 and 71 formed onthe LTCC substrate 11. The LED chips 4 are electrically connected toeach of the external connection terminals 81 and 71 via bonding wires W.The LED chips 4, the external connection terminals 81 and 71, and thebonding wires W are sealed with a luminescent material-containingsealing resin 62. The LTCC substrate 11 includes multiple (ten) LTCClayers 11 a to 11 j, and a plurality of heat-radiating vias 21 made ofsilver are each formed so as to pass through the layers of the LTCCsubstrate 11, i.e., so as to extend in a direction perpendicular to theLTCC substrate 11, and are each connected to the silver reflecting layer2. Further, the external connection terminals 81 and 71 are respectivelyconnected to two wiring vias (heat-radiating vias) 22 passing throughthe LTCC substrate 11, and the wiring vias 22 are respectively connectedto external terminals 82 and 72 formed on the underside of the LTCCsubstrate 11. It should be noted here that the LTCC substrate 10 is madeby stacking ten green sheets. The present embodiment has four LED chips4 placed therein. However, for simplicity, FIG. 9 shows a cross-sectionof a single LED chip.

The following shows a method for manufacturing a light-emittingapparatus 1003.

Step (1): Raw material is prepared by blending/mixing ceramic powder(Al₂O₃ powder, 30 wt %) and glass powder (borosilicate glass powder, 70wt %) with a given ratio. To the raw material thus mixed, an organicbinder (acrylic resin) and a solvent (toluene) are added, and thendispersed uniformly. Thus made is material, called slurry, which servesas a basis for a green sheet. The slurry is applied onto a PET film by adoctor blade molding machine so as to have a given thickness, and thenreeled off after a drying step. A sheet-like material thus made iscalled a green sheet (thickness of 0.1 mm). The green sheet is cut tothe proper size, and then subjected to a process (punching process) ofmaking holes that are to serve as heat-radiating vias 21 and wiring vias22. The holes that are to serve as heat-radiating vias 21 and wiringvias 22 are filled with material (silver paste). Thus made is a singleLTCC layer (thickness 0.1 mm). Ten LTCC layers (11 a, 11 b, 11 c, 11 d,11 e, 11 f, 11 g, 11 h, 11 i, 11 j) thus made are stacked,pressure-bonded by heat, and then subjected to a firing step (850° C.).Thus made is an LTCC substrate 11.

Step (2): On the LTCC substrate 11 (thickness 1 mm), a silver film 2(thickness 0.25 mm) is formed by plating, whereby a silver reflectinglayer 2 is formed. It should be noted here that the green sheet is madeof glass powder of borosilicate glass (Na₂O—B₂O₃—SiO₂) and ceramicpowder of Al₂O₃.

Step (3): On the silver reflecting layer 2, a glass layer 3 (thickness0.007 mm) is formed. It should be noted here that the glass layer 3 ismade of transparent borosilicate glass (Na₂O—B₂O₃—SiO₂) with use of adoctor blade method.

Step (4): On the wiring vias 22 of the LTCC substrate 11, externalconnection terminals 81 and 71 (thickness 0.7 mm, width 0.45 mm) areformed with gold by screen printing so that the glass layer 3 isinterposed between the external connection terminals 81 and 71.

Step (5): On the glass layer 3, LED chips 4 (shorter-side width 0.24 mm,longer-side width 0.48 mm, thickness 0.14 mm, quantity 4) are fixed withuse of silicone resin (not illustrated). The LED chips 4 and theexternal connection terminals 81 and 71 are electrically connected withuse of bonding wires W.

Step (6): Next, a sealing resin (silicone) 62 containing a luminescentmaterial (Eu:BOSE) is formed, and the luminescent material-containingsealing resin 62 is cured by heat. The luminescent material-containingsealing resin 62 is formed by keeping a mixture of a luminescentmaterial and silicone resin that is a transparent resin at 150° C. over30 minutes and curing the resin. It should be noted that, in the presentembodiment, the luminescent material-containing sealing resin 62 isformed so as to give off light corresponding to the point(x,y)=(0.345,0.35) on the CIE chromaticity diagram. Thus, thelight-emitting section is manufactured.

It should be noted here that heat from the LED chips 4 is transferred tothe external connection terminals 81 and 71 via the bonding wires W. Theexternal terminals 82 and 72, formed on the underside of the LTCCsubstrate 11, are connected to the external connection terminals 81 and71 via the wiring vias 22, respectively, so that the heat transferred tothe external connection terminals 81 and 71 is transferred to theexternal terminals 82 and 72 to be radiated. This effect is moreremarkable because the contact between the external connection terminals81 and 71 and the wiring vias 22 allows the heat generated by the LEDchips 4 to be efficiently transferred to the wiring vias 22 via thebonding wires W. The wiring vias 22 can be made of any metal, as well assilver. Alternatively, as with the silver reflecting layer 2, the wiringvias 22 may be made of a silver alloy (AgPt, Ag—Bi, Ag—Nd based alloy)composed mainly of silver. It is because the glass layer 3 covers onlythe silver reflecting layer 2 that the wiring vias 22 can be provided tobe connected to the external connection terminals 81 and 71 on the LTCCsubstrate 11.

It should be noted here that the silver reflecting layer 2 is effectivein taking out light emitted by the LED chips 4 toward the LTCC substrate11. Further, in the present embodiment, the silver reflecting layer 2 iscovered with the glass layer 3. This makes it possible to inhibit thereflecting layer from being altered, deteriorating, and decreasing inreflectance. The glass layer 3 is more highly isolating against oxygen,moisture, or the like than a common resin is, and therefore can suppressa change over time in the silver reflecting layer 2.

It is here possible to place a heat sink (not illustrated) on theunderside of the LTCC substrate 11 of the light-emitting apparatus 1003.In such a case, it is preferable that the heat-radiating vias 21 be incontact with the heat sink.

Embodiment 5

FIG. 10 is a cross-sectional view schematically illustrating alight-emitting apparatus 1004 according to another embodiment of thepresent invention. For convenience of explanation, members having thesame functions as those used in Embodiment 4 are given the samereference numerals, and will not be described below. The light-emittingapparatus 1004 includes: an alumina substrate 12; a silver reflectinglayer 2 formed on the alumina substrate 12; a glass layer 3 coveringonly the silver reflecting layer 2; LED chips 4 placed on the glasslayer 3; and positive and negative electrode external connectionterminals 81 and 71 formed on the alumina substrate 12. The LED chips 4are electrically connected to each of the external connection terminals81 and 71 via bonding wires W. The LED chips 4, the bonding wires W, andthe external connection terminals 81 and 71 are sealed with aluminescent material-containing sealing resin 62; however, theluminescent material-containing sealing resin 62 does not cover thewhole surface of the alumina substrate 12 across the depth of FIG. 10.The alumina substrate 12 has unsealed regions thereon via which thepositive and negative external connection lands 81 and 71 are exposed toenable connection to an external power supply (not illustrated). Thepresent embodiment has 36 LED chips 4 placed therein. However, forsimplicity, FIG. 10 shows a cross-section of a single LED chip.

The following shows a method for manufacturing a light-emittingapparatus 1004.

Step (1): On an alumina substrate 12 (thickness 2 mm), a silver film 2(thickness 0.2 mm) is formed by plating, whereby a silver reflectinglayer 2 is formed.

Step (2): On the silver reflecting layer 2, a glass layer 3 (thickness0.006 mm) is formed. It should be noted here that the glass layer 3 ismade of transparent borosilicate glass (Na₂O—B₂O₃—SiO₂) with use of adoctor blade method.

Step (3): On the alumina substrate 12, external connection terminals 71and 81 (thickness 0.7 mm, width 0.45 mm, length 2 mm) are formed byscreen printing.

Step (4): On the glass layer 3, LED chips 4 (shorter-side width 0.24 mm,longer-side width 0.48 mm, thickness 0.14 mm, quantity 36) are fixedwith use of silicone resin (not illustrated). Next, the LED chips 4 andthe external connection terminals 71 and 81 are electrically connectedwith use of bonding wires W.

Step (5): Next, a sealing resin (silicone) 62 containing a luminescentmaterial (Eu:BOSE) is injected, and the luminescent material-containingsealing resin 62 is cured by heat. The luminescent material-containingsealing resin 62 is formed by keeping a mixture of a luminescentmaterial and silicone resin that is a transparent resin at 150° C. over30 minutes and curing the resin. It should be noted that, in the presentembodiment, the luminescent material-containing sealing resin 62 isformed so as to give off light corresponding to the point(x,y)=(0.345,0.35) on the CIE chromaticity diagram. Thus, thelight-emitting section is manufactured.

Further, in the present embodiment, the silver reflecting layer 2 iscovered with the glass layer 3. This makes it possible to inhibit thereflecting layer from being altered, deteriorating, and decreasing inreflectance. The glass layer 3 is more highly isolating against oxygen,moisture, or the like than a common resin is, and therefore can suppressa change over time in the silver reflecting layer 2.

Further, it is preferable that the external connection terminals 81 and71 on the glass layer 3 be made of a material containing gold, which ischemically stable.

In each of the embodiments, examples of the glass powder of which theglass layer and the LTCC substrate are made encompass silica glass,soda-lime glass, borosilicate glass, aluminoborosilicate glass,borosilicate zinc glass, aluminosilicate glass, and/or phosphate glass.Particular preference is given to borosilicate glass.

Further, examples of the ceramic powder of which the LTCC substrate ismade encompass SiO₂, Al₂O₃, ZrO₂, TiO₂, ZnO, MgAl₂O₄, ZnAl₂O₄, MgSiO₃,MgSiO₄, Zn₂SiO₄, Zn₂TiO₄, SrTiO₃, CaTiO₃, MgTiO₃, BaTiO₃, CaMgSi₂O₆,SrAl₂Si₂O₈, BaAl₂Si₂O₈, CaAl₂Si₂O₈, Mg₂Al₄Si₅O₁₈, Zn₂Al₄Si₅O₁₈, AlN,SiC, mullite, and zeolite. Further, the LTCC substrate can be replacedby a substrate based on ceramic.

The sealing resin is suitably made of either (i) a highlyweather-resistant transparent resin such as epoxy resin, urea resin, orsilicone resin, or (ii) a highly light-resistant translucent inorganicmaterial such as silica sol or glass. Further, the sealing resin maycontain a diffusing agent together with the luminescent material. Asuitably usable specific example of the diffusing agent is bariumtitanate, titanium oxide, aluminum oxide, silicon oxide, calciumcarbonate, silicon dioxide, or the like.

The LED chips are blue LED chips each including a sapphire substrate andgallium nitride-based light-emitting section formed on the sapphiresubstrate.

A suitably usable example of the luminescent material is a Ce:YAG(cerium-activated yttrium-aluminum-garnet) luminescent material, aEu:BOSE or SOSE (europium-activated strontium-barium-orthosilicate)luminescent material, a europium-activated a sialon luminescentmaterial, or the like.

It should be noted that it is possible to drip a molding sealing resinin forming the resin sealer (luminescent material-containing sealingresin). Further, it is possible to form the resin sealer with use of amold, and the resin sealer can be shaped, for example, into an upwardlyconvex hemisphere so as to function as a lens.

It should be noted here that the LED chips can be joined with athermosetting resin (adhesive resin) or the like. Specific examplesinclude silicone resin, epoxy resin, acrylic resin, and imide resin.

In each of the embodiments described above, the LED chips used are blueLED chips each composed of a gallium nitride-based compoundsemiconductor. However, the LED chips used may be blue LED chips eachcomposed of a ZnO (zinc oxide)-based compound semiconductor.Alternatively, the LED chips used may be LED chips of an InGaAlP- orAlGaAs-based compound semiconductor.

In each of the embodiments, each of the LED chips has P- and N-sideelectrodes formed on one surface thereof and the surface serves as anupper surface to which two bonding wires are connected. However, the LEDchip is not necessarily connected in such a way. It is possible to forma wire on the glass layer and connect the LED chip directly to the wire,for example, by soldering. Further, although the LED chips have beendescribed as emitting blue light, the color of light that is emitted bythe LED chips is not limited to blue. For example the LED chips may emitultraviolet light or green light. Further, although a method to obtainwhite by converting, with a luminescent material, light emitted by theLED chips has been described, it is possible to obtain a color requiredfor illumination, such as white or the color of light emitted by a lightbulb, by using three-color (red, green, and blue) LED chips instead ofusing a luminescent material.

Embodiment 6

(Light-Emitting Apparatus)

FIGS. 13( a) and 13(b) shows a plan view and a cross-sectional view,respectively, illustrating a structure of a light-emitting apparatus ofEmbodiment 6. In FIG. 13( b), the light-emitting apparatus 2001includes: a package 110 including a cup-shaped depressed portion 108; anLED chip 112; and a luminescent material 114. The LED chip 112 isdie-bonded to a chip-mounting portion 113 located substantially in thecenter of the bottom surface of the depressed portion 108. The LED chip112 is covered with a sealing resin 116 in which the luminescentmaterial 114 has been dispersed. The LED chip 112 emits primary light(e.g., blue light, having a luminescence peak in a blue-wavelengthregion, whose wavelength ranges from not less than 400 nm to not morethan 500 nm). The luminescent material 114 emits secondary light (e.g.,yellow light, having a luminescence peak in a yellow-wavelength region,whose wavelength ranges from not less than 550 nm to not more than 600nm) when excited by the primary light. The primary light and thesecondary light are mixed together so as to be emitted as white lightfrom an exit face 118 facing toward an open side of the depressedportion 108.

The internal and bottom surfaces of the depressed portion 108 arecovered with a silver reflecting layer 120 made of metal such as Ag, soas to have high reflectance, and are further covered with a glass layer121 so that the reflectance can be maintained for a long period of time.

In FIG. 13( a), the bottom surface of the depressed portion 108 includesa pair of electrode pads 123. The pair of electrode pads 123 are formedby spacing one portion of the silver reflecting layer 120 from another.The LED chip 112 is die-bonded to the chip-mounting portion 113, and theelectrode pads 122 of the LED chip 112 and the electrode pads 123 of thepackage 110 are electrically connected by wire bonding. It should benoted that each of the electrode pads 123 has a portion to which a wireW is connected and whose surface is exposed, and is not covered with theglass layer 121.

In FIG. 13( b), the lower surface of the light-emitting apparatus 2001is a mounting surface 126 that faces a mounted substrate (notillustrated), and the mounting surface 126 has external connectionterminals 128 formed thereon, with conducting vias 130 interposedbetween the electrode pads 123 and the external connection terminals128. The vias 130 form a current pathway to the LED chip 112 when theexternal connection terminals 128 are connected to a wiring patternformed on the mounted substrate.

(Manufacturing Method)

The following describes a method for manufacturing a light-emittingapparatus 2001. FIG. 14 is a flow chart illustrating a method formanufacturing a light-emitting apparatus. FIGS. 15( a) through 15(d) arecross-sectional views illustrating how a stack is arranged. FIGS. 16( a)through 16(d) are cross-sectional views illustrating a method formanufacturing a light-emitting apparatus.

The following first describes a method for forming a package. A packageaccording to the present embodiment is a low temperature co-firedceramic (LTCC) package. The package is formed by firing a stack ofsheet-like materials, called green sheets, which have been subjected,for example, to a process of making holes in the green sheets and aprocess of filling the holes with paste.

The following first describes a method for forming a green sheet 150.Material called slurry is prepared by blending an organic binder and asolvent with a main material, i.e., a mixture of alumina ceramic powderand glass, and by uniformly dispersing the organic binder and thesolvent in the mixture. Next, the slurry is applied onto a PET film by afilm-forming apparatus so as to have a given thickness, and then reeledoff after a drying step. Thus obtained is a green sheet 150. Next, thegreen sheet 150 is cut to a predetermined size, and then subjected, forexample, to a process of making holes in those portions of the greensheet 150 in which components of a package 110 such as a depressedportion 108, vias 130, electrode pads 123, and a glass layer 121 are tobe formed and a process of filling the holes with paste. A plurality ofsuch green sheets 150 are aligned with one another and stacked. Thusformed is a stack 155 (FIG. 15( d)).

For example, as illustrated in FIGS. 15( a) through 15(d), the via 130,the electrode pad 123, and the chip-mounting portion 113 are formed bystacking green sheets (FIG. 15( a)) whose holes have been filled withmetal paste in which metal such as Ag has been dispersed. The metalpaste is conductive between vertically adjacent layers, so that theelectrode pad 123 and the external connection terminal 128 areelectrically conductive with each other. Further, the pair of electrodepads 123 are spaced from each other so as to be insulated and separatedfrom each other.

The glass layer 121 is formed by lamination or adhesion of a layer ofglass paste onto a layer of metal paste. For example, the glass layer121 is formed by covering the silver reflecting layer 120 with a greensheet (FIG. 15( b)) whose hole has been filled with glass paste to forma chip-mounting portion 113.

It should be noted that each of the electrode pads 123 has a surfaceexposed without being covered with glass. This portion is formed bystacking a green sheet (FIGS. 15( b) and 15(c)) having a hole, providedin a portion filled with glass paste, via which the surface of theelectrode pad 123 is to be exposed. Since the surface of the electrodepad 123 is exposed, preference is given to material that is hard to bealtered, and the metal paste is preferably made of Au paste or the like.

In order that a plurality of packages 110 are formed simultaneously, agreen sheet 150 is formed repeatedly with a plurality of processedpatterns subjected to a process of making holes and a process of fillingthe holes with paste.

Next, the stack 155 is fired at 700° C. to 1,000° C., e.g., at 850° C.to 900° C., whereby the alumina powder of which the green sheets 150 aremade, the metal paste of which the silver reflecting layer 120 is made,the glass paste covering the silver reflecting layer 120, the Au pasteof which the electrode pads 123 are made are co-fired, with the resultthat a package 110 is completed. At this time, the glass componentcontained in the glass paste is melted to smoothly cover a surface ofthe silver reflecting layer 120. Further, the co-firing of the rawmaterials brings about an effect of alleviating stress on the interfacebetween one layer and another.

It should be noted that the layers constituting the package 110 can beformed, for example, so that the layer extending from the chip-mountingportion 113 to the mounting surface 126, the silver reflecting layer120, and the glass layer 121 have a thickness of 0.5 mm, a thickness of0.005 mm, and a thickness of 0.01 mm, respectively.

Referring to FIGS. 16( a) through 16(d), the following describes stepsto be taken after an LED chip 112 is mounted. It should be noted thatFIGS. 16( a) through 16(d) do not illustrate a via 130.

Brazing material (not illustrated) such as silicone paste is applied tothe chip-mounting portion 113 of each depressed portion 108 of a stack155 that has been fired, and then an LED chip 112 are die-bonded ontothe chip-mounting portion 113. Next, the electrode pads 122 of the LEDchip 112 and the electrode pads 123 of the package 110 are connected bywire bonding, respectively. At this time, the electrode pads 123 of thepackage 110 have not been covered with glass, and therefore can bewire-bonded satisfactorily (FIGS. 16( a) and 16(b)).

Next, the depressed portion 108 is filled with a sealing resin 116 inwhich a luminescent material 114 has been dispersed in advance, and thesealing resin 116 is cured, whereby the LED chip 112 is covered. Thesealing resin 116 can be suitably made of dimethyl silicone or methylrubber, which is highly heat-resistant and highly adhesive to glass. Forexample, in cases where KER2500 (manufactured by Shin-Etsu Chemical Co.,Ltd.) is used as dimethyl silicone, the sealing resin is cured at 100°C. for 60 minutes, and after-cured at 150° C. for 300 minutes. Dimethylsilicone and methyl rubber are lower in gas sealing properties thanorganic modified silicone or the like. However, since the surface of thesilver reflecting layer 120 is covered with glass, the surface can beinhibited from being altered.

Finally, the stack 155 is divided into individual light-emittingapparatuses. The division is performed, for example, by using a UVsheet, i.e., by attaching a UV sheet 158 to the mounting surface 126,placing the stack 155 on a stage, and dicing the stack 155 alongpredetermined positions. Next, the adhesive of the UV sheet 158 is curedby UV light irradiation, and then the individual pieces are separatedfrom one another.

According to the aforementioned arrangement, because of a high degree ofadhesion between dimethyl silicone or methyl rubber and glass, thesealing resin 116 can be inhibited from being detached from the glasslayer 121 covering the silver reflecting layer 120. A possible reasonfor the high degree of adhesion is that the glass surface has a hydroxylgroup exposed thereon and therefore has high binding force with respectto silicone resin. Another possible reason is that dimethyl silicone andmethyl rubber are higher in elasticity than organic modified silicone orthe like and therefore easily absorb a change in volume such as thermalexpansion or contraction.

Further, it is preferable that the sealing resin 116 has a continuouslyallowable temperature limit of not less than 120° C. It should be notedhere that in cases where the thermal resistance of a package 110 is 200°C./W and the heat of an LED chip 112 is 0.06 W, the rise in temperatureof the package 110 is at most 12° C. However, the light-emittingapparatus 2001 is required to serve for a very long period of time,e.g., 40,000 hours. For the purpose of satisfying such reliability, sucha continuously allowable temperature limit as above is required.

It should be noted that the luminescent material 114 can be suitablyrealized, for example, by BOSE (Ba, O, Sr, Si, Eu) or the like.Alternatively, the luminescent material 114 can be suitably realized bySOSE (Sr, Ba, Si, O, Eu), YAG (cerium-activatedyttrium-aluminum-garnet), a sialon ((Ca), Si, Al, O, N, Eu), β sialon(Si, Al, O, N, Eu), or the like, as well as BOSE. Further, when the LEDchip 112 is realized by using an ultraviolet (near-ultraviolet) LED, forexample, whose peak wavelength ranges from 390 nm to 420 nm, instead ofusing a blue LED, a further improvement in luminous efficiency can beachieved.

As stated above, a light-emitting apparatus 2001 including a silverreflecting layer 120 and a glass layer 121 covering the silverreflecting layer 120 and sealed with silicone resin is highly reliablebecause of a combination of high gas sealing properties, high heatresistance, and a high degree of adhesion.

The present embodiment is arranged such that the sealing resin 116 has aluminescent material 114 dispersed therein, but is not necessarilylimited to this. For example, the present embodiment may be arrangedsuch that the sealing resin 116 covers a luminescent material 114covering only the vicinity of an LED chip 112, or may be arranged suchthat the sealing resin 116 does not include a luminescent material 114.Further, although the silver reflecting layer 120 is formed not only onthe inner wall of the depressed portion 108 but also on a portioncorresponding to a bank 131 circularly surrounding the periphery of theexit face 118, the present embodiment may be arranged such that thesilver reflecting layer 120 is not formed on the portion correspondingto the bank 131. In other words, as long as the present embodiment isarranged such that the glass layer 121 is interposed between the sealingresin 116 and the surface of the silver reflecting layer 120 on thepackage 110, an improvement in reliability can be achieved.

Embodiment 7

FIG. 17 is a cross-sectional view illustrating a structure of alight-emitting apparatus of Embodiment 7. The light-emitting apparatus2002 includes a luminescent material-containing glass layer 160 in whicha luminescent material 114 has been dispersed, instead of including aglass layer 121. The primary light, which is blue light emitted by anLED chip 112, and the secondary light, which is yellow light emitted bythe luminescent material 114 being excited by the primary light, aremixed together so as to be emitted as white light from an exit face 118facing toward an open side of the depressed portion 108.

The light-emitting apparatus 2002 is equivalent to Embodiment 6 exceptthat the luminescent material-containing glass layer 160 is formed bylamination or adhesion of a layer of luminescent material-containingglass paste onto a layer of metal paste. It should be noted that theluminescent material-containing glass paste is obtained by dispersingthe luminescent material 114 such as the aforementioned BOSE, SOSE, YAG,a sialon, or β sialon in glass powder.

According to the present embodiment, since the luminescent material 114hardly settles at the bottom of the luminescent material-containingglass paste, the density of the luminescent material 114 in theluminescent material-containing glass layer 160 can be furtheruniformed. This makes it possible to suppress variations in chromaticityof emitted light. A possible reason for the little sedimentation of theluminescent material 114 is that the glass powder contained in theluminescent material-containing glass paste exhibits a function ofsuppressing sedimentation of the luminescent material 114.

In FIG. 17, the sealing resin 116 has no luminescent material 114dispersed therein. However, the sealing resin 116 can be arranged tohave a luminescent material 114 dispersed therein.

Further, the luminescent material-containing glass layer 160 can beformed to wholly or partially contain a luminescent material.Preferably, as illustrated in FIG. 17, the luminescentmaterial-containing glass layer 160 is formed to contain a luminescentmaterial in a portion making contact with the sealing resin 116 and tocontain no luminescent material in the portion corresponding to the bank131. This makes it possible to inhibit the luminescent material 114 frombeing excited by external light on the bank 131 to emit yellow light.

Embodiment 8

FIG. 18 is a cross-sectional view illustrating a structure of alight-emitting apparatus of Embodiment 8. The present embodiment ischaracterized in that the bottom surface of the depressed portion 108 ofthe package 110 is provided with recessed areas, that a bottom surfaceof each of the recessed areas is formed with an electrode pad 123, andthat an insulating layer 132 is interposed between the electrode pad 123and the silver reflecting layer 120. The present embodiment is otherwiseequivalent to Embodiment 6.

In the vicinity of each electrode pad 123 of the package 110, theceramic of which the package 110 is made is exposed in order to insulateone of the electrode pads 123 from the other by surrounding eachelectrode pad 123. Therefore, this area leaks a portion of emittedlight, thus causing a decrease in emission efficiency. In thelight-emitting apparatus 2001 of Embodiment 6, the exposed portion ofthe ceramic is formed at substantially the same level as thechip-mounting portion 113. Meanwhile, in the present embodiment, theexposed portion of the ceramic exists in a further recessed part of therecessed area that is hard for emitted light to reach. This inhibitslight from leaking from the exposed portion of the ceramic in thevicinity of each electrode pad 123, thus making it possible to achievean improvement in efficiency with which light is taken out.

Embodiment 9

FIGS. 19( a) and 19(b) are pattern diagrams illustrating a structure ofa surface light source of Embodiment 9. The surface light source 2004 inthe present embodiment includes: a light-emitting apparatus 305 arrangedas set forth in any one of Embodiments 6 to 8; and an optical waveguide310 that guides light emitted by the light-emitting apparatus 305 andcauses the light to be emitted by an exit face 316 in the form of planeemission, the light-emitting apparatus 305 having an exit face 118disposed just in front of an entrance end face 312 of the opticalwaveguide 310. It should be noted that refraction or the like on theentrance end face 312 of the optical waveguide 310 is omitted from theillustrations.

The light emitted by the light-emitting apparatus 305 illuminates theentrance end face 312, but is partially reflected by the entrance endface 312 and a dead end face 314 of the optical waveguide 310 andreturned to the exit face 118 of the light-emitting apparatus 305.Meanwhile, the silver reflecting layer 120 of the light-emittingapparatus 305 is formed not only on the inner wall of the depressedportion 108 but also on a portion corresponding to a bank 131 circularlysurrounding the periphery of the exit face 118. Therefore, a reflectionof emitted light reflected by the entrance end face 312 of the opticalwaveguide 310 and a return of emitted light reflected back from the deadend face 314 of the optical waveguide 310 can be again reflected to beincident. This results in an increase in efficiency in the use of light.

The present invention can be applied to an illuminating apparatus or abacklight of a liquid crystal display.

A light-emitting apparatus according to an embodiment of the presentinvention has (i) at least one semiconductor device which emits lighttoward a higher position than a substrate and (ii) a plurality ofexternal connection terminals, and includes: a light-reflecting layer,provided on the substrate, which reflects the light emitted by the atleast one semiconductor device; and a covering layer which covers atleast the light-reflecting layer and which transmits the light reflectedby the light-reflecting layer. The at least one semiconductor device isprovided on the covering layer, and is electrically connected to theexternal connection terminals via connecting portions, and the at leastone semiconductor device and the connecting portions are sealed with asealing resin so as to be covered.

According to the foregoing arrangement, the light-reflecting layerreflects light emitted by the semiconductor device toward a lowerposition (toward the substrate), thereby enabling effective use of theemitted light with a reduction in loss of the emitted light. This makesit possible to increase the amount of light that is emitted by thelight-emitting apparatus, and the covering of the light-reflecting layerwith the covering layer brings about an effect of inhibiting thelight-reflecting layer from being altered or deteriorating and,furthermore, from decreasing in reflectance due to the alteration ordeterioration.

It is preferable that the light-reflecting layer have an opticalreflectance of not less than 90%.

According to the foregoing arrangement, the high optical reflectance ofthe light-reflecting layer enables an increase in the amount of lightthat is emitted by the light-emitting apparatus.

It is preferable that the light-reflecting layer be made of silver or asilver alloy composed mainly of silver.

According to the foregoing arrangement, the formation of thelight-reflecting layer from silver or a silver alloy causes heatgenerated by the semiconductor device to be diffused in a directionalong a surface of the substrate, thus enabling an enhancement in heatradiation properties of the light-emitting apparatus. This makes itpossible to inhibit a color shift from being caused by heat generated bythe light-emitting apparatus.

In an embodiment of the light-emitting apparatus, the substrate may bebased on ceramic. Furthermore, the substrate may be based on lowtemperature co-fired ceramic.

Since the low temperature co-fired ceramic is higher in thermalconductivity than a common organic material, the foregoing arrangementenables a further enhancement in heat radiation properties of thelight-emitting apparatus, thus making it possible to integratesemiconductor devices.

In an embodiment of the light-emitting apparatus, it is preferable thatthe substrate be a product of firing of glass powder and ceramic powderas materials. The glass powder can be realized by glass powdercontaining silica glass, soda-lime glass, borosilicate glass,aluminoborosilicate glass, borosilicate zinc glass, aluminosilicateglass, or phosphate glass. Further, the ceramic powder can be realizedby ceramic powder containing SiO₂, Al₂O₃, ZrO₂, TiO₂, ZnO, MgAl₂O₄,ZnAl₂O₄, MgSiO₃, MgSiO₄, Zn₂SiO₄, Zn₂TiO₄, SrTiO₃, CaTiO₃, MgTiO₃,BaTiO₃, CaMgSi₂O₆, SrAl₂Si₂O₈, BaAl₂Si₂O₈, CaAl₂Si₂O₈, Mg₂Al₄Si₅O₁₈,Zn₂Al₄Si₅O₁₈, AlN, SiC, mullite, or zeolite.

In an embodiment of the light-emitting apparatus, the covering layer ismade of glass, and the glass can be realized by glass containing silicaglass, soda-lime glass, borosilicate glass, aluminoborosilicate glass,borosilicate zinc glass, aluminosilicate glass, or phosphate glass.

According to the foregoing arrangement, the substrate and the coveringlayer contains glass powder. This improves adhesion between thesubstrate and the covering layer and further inhibits a change over timefrom being caused by deterioration or the like in the light-reflectinglayer, thus enabling suppression of a decrease in reflectance. Inparticular, borosilicate glass (NA₂O—B₂O₃—SiO₂) is low in coefficient ofthermal expansion, high in thermal shock temperature, and highlychemically resistant because of its high content of boron oxide, thusbeing further highly effective in protecting the light-reflecting layer.

In an embodiment of the light-emitting apparatus, the at least onesemiconductor chip may be a light-emitting diode chip. The coveringlayer may be made of glass. The connecting portions may include wiringpatterns and bonding wires. The wiring patterns may be provided on thesubstrate or on the covering layer in parallel with one another and atdistances from one another. The at least one semiconductor chip mayinclude a plurality of semiconductor chips placed between the wiringpatterns. The wiring patterns and the semiconductor devices may beconnected via the bonding wires.

The foregoing arrangement makes it possible to freely adjust the numberof semiconductor devices, thus making it easy to adjust the luminance ofthe light-emitting apparatus, to adjust the chromaticity of thelight-emitting apparatus, and to take measures against heat generated bythe light-emitting apparatus.

In an embodiment of the light-emitting apparatus, it is preferable thatthe substrate contain heat-radiating vias, made of metal, which arejoined to the light-reflecting layer, the external connection terminals,or both.

According to the foregoing arrangement, the heat-radiating via connectedto the light-reflecting layer or the external connection terminalsenable a further enhancement in heat radiation properties of thelight-emitting apparatus.

It is preferable that the heat-radiating vias extend in a directionperpendicular to a surface of the substrate.

Furthermore, it is preferable that the heat-radiating vias be made ofsilver or a silver alloy composed mainly of silver.

In addition to the radiation of heat by the light-reflecting layer in adirection along a plane of the substrate, the foregoing arrangementenhances radiation of heat in a direction perpendicular to thesubstrate. This makes it possible to integrate semiconductor deviceswithin a small region.

In an embodiment of the light-emitting apparatus, it is preferable thatthe wiring patterns be made of gold.

According to the forgoing arrangement, the formation of the wiringpatterns from gold makes it possible to inhibit a change over time frombeing caused by deterioration or the like in the wiring patterns.

In an embodiment of the light-emitting apparatus, it is preferable thata nickel or chrome layer be provided between the wiring patterns and thecovering layer.

The foregoing arrangement improves adhesion between the covering layermade of glass and the wiring patterns, thus making it possible toinhibit a change over time from being caused by deterioration or thelike in the wiring patterns.

In an embodiment of the light-emitting apparatus, the at least onesemiconductor device may be placed on the covering layer via an adhesiveresin.

In an embodiment of the light-emitting apparatus, it is preferable thatthe sealing resin contain a luminescent material.

According to the foregoing arrangement, the luminescent material absorbslight emitted by the semiconductor device and emits light of a differentwavelength. This makes it possible to achieve, by using a semiconductordevice that emits a single type of light, a light-emitting apparatusthat emits a different type of light (e.g., white light).

In an embodiment of the light-emitting apparatus, it is preferable thatthe sealing resin be constituted by a luminescent material-containingresin section containing a luminescent material and a transparent resinsection provided so as to cover the luminescent material-containingresin section.

The foregoing arrangement makes it possible to protect the luminescentmaterial-containing resin section by the transparent resin section.

In an embodiment of the light-emitting apparatus, it is preferable thatthe sealing resin have a domed contour.

In an embodiment of the light-emitting apparatus, it is preferable thatthe luminescent material-containing resin section and the transparentresin section both have domed contours.

According to the foregoing arrangement, the sealing resin has no sharpand definite corners pointing in a direction of light radiation, thuscausing continuous changes in direction in which irradiating light isrefracted. This brings about an effect of making it possible to reduceunevenness in intensity of the irradiating light.

An embodiment of a light-emitting apparatus includes: a light-emittingdiode chip; a package, including a chip-mounting portion and a silverreflecting layer which reflects light emitted by the light-emittingdiode chip, in which the light-emitting diode chip is die-bonded to thechip-mounting portion; and a sealing resin which covers thelight-emitting diode chip, the silver reflecting layer being coveredwith a glass layer.

In an embodiment of the light-emitting apparatus, it is preferable thatthe sealing resin be made of dimethyl silicone or methyl rubber.

In an embodiment of the light-emitting apparatus, it is preferable thatthe sealing resin have a luminescent material dispersed therein forabsorbing at least a portion of primary light emitted by thelight-emitting diode chip and converting the primary light intosecondary light having a longer wavelength than the primary light.

In an embodiment of the light-emitting apparatus, it is preferable thatthe silver reflecting layer is provided on a periphery of an exit faceof the light-emitting apparatus.

In an embodiment of the light-emitting apparatus, it is preferable thatthe chip-mounting portion be provided with a recessed area whose bottomsurface is provided with an electrode pad.

A method according an embodiment of the present invention formanufacturing a package for a light-emitting apparatus includes thesteps of: preparing a plurality of green sheets made mainly of alumina;performing a process of making holes in the plurality of green sheets;filling the holes of the plurality of green sheets with at least eithermetal paste or glass paste; and stacking and firing the plurality ofgreen sheets so that the metal paste is covered with the glass paste,the steps being executed in the order presented.

The embodiments and concrete examples of implementation discussed in theforegoing detailed explanation serve solely to illustrate the technicaldetails of the present invention, which should not be narrowlyinterpreted within the limits of such embodiments and concrete examples,but rather may be applied in many variations within the spirit of thepresent invention, provided such variations do not exceed the scope ofthe patent claims set forth below.

The invention claimed is:
 1. A light-emitting apparatus having at leastone semiconductor device which emits light toward a higher position thana substrate and a plurality of external connection terminals, thelight-emitting apparatus comprising: a light-reflecting layer, providedon the substrate, which reflects the light emitted by the at least onesemiconductor device; and a covering layer which covers at least thelight-reflecting layer and which transmits the light reflected by thelight-reflecting layer, the at least one semiconductor device having atop surface and a bottom surface, being provided on the covering layerso that the bottom surface faces the covering layer and beingelectrically connected to the external connection terminals viaconnecting portions, the covering layer covering the entire bottomsurface of the at least one semiconductor device, the at least onesemiconductor device and the connecting portions being sealed with asealing resin so as to be covered, wherein the light-reflecting layer isnot connected to any of the external connection terminals, the coveringlayer covers a side surface of the light-reflecting layer, and thelight-emitting apparatus comprises a plurality of semiconductor devicesemitting light, and the light-reflecting layer is a single continuouslayer that covers bottom surfaces of all of the semiconductor devices.2. The light-emitting apparatus as set forth in claim 1, wherein thelight-reflecting layer has an optical reflectance of not less than 90%.3. The light-emitting apparatus as set forth in claim 1, wherein thelight-reflecting layer is made of silver or a silver alloy composedmainly of silver.
 4. The light-emitting apparatus as set forth in claim1, wherein the substrate is based on ceramic.
 5. The light-emittingapparatus as set forth in claim 4, wherein the substrate is based on lowtemperature co-fired ceramic.
 6. The light-emitting apparatus as setforth in claim 5, wherein the low temperature co-fired ceramic is aproduct of firing of glass powder and ceramic powder as materials. 7.The light-emitting apparatus as set forth in claim 6, wherein the glasspowder contains silica glass, soda-lime glass, borosilicate glass,aluminoborosilicate glass, borosilicate zinc glass, aluminosilicateglass, or phosphate glass.
 8. The light-emitting apparatus as set forthin claim 6 or 7, wherein the ceramic powder contains SiO₂, Al₂O₃, ZrO₂,TiO₂, ZnO, MgAl₂O₄, ZnAl₂O₄, MgSiO₃, MgSiO₄, Zn₂SiO₄, Zn₂TiO₄, SrTiO₃,CaTiO₃, MgTiO₃, BaTiO₃, CaMgSi₂O₆, SrAl₂Si₂O₈, BaAl₂Si₂O₈, CaAl₂Si₂O₈,Mg₂Al₄Si₅O₁₈, Zn₂Al₄Si₅O₁₈, AlN, SiC, mullite, or zeolite.
 9. Thelight-emitting apparatus as set forth in claim 1, wherein: the coveringlayer is made of glass; and the glass contains silica glass, soda-limeglass, borosilicate glass, aluminoborosilicate glass, borosilicate zincglass, aluminosilicate glass, or phosphate glass.
 10. The light-emittingapparatus as set forth in claim 1, wherein: the at least onesemiconductor chip is a light-emitting diode chip; and the coveringlayer is made of glass; and the connecting portions include wiringpatterns and bonding wires; and the wiring patterns are provided on thesubstrate or on the covering layer in parallel with one another and atdistances from one another; and the at lease one semiconductor chipincludes a plurality of semiconductor chips placed between the wiringpatterns; and the wiring patterns and the semiconductor devices areconnected via the bonding wires.
 11. The light-emitting apparatus as setforth in claim 10, wherein the wiring patterns are made of gold.
 12. Thelight-emitting apparatus as set forth in claim 11, wherein a nickel orchrome layer is provided between the wiring patterns and the coveringlayer.
 13. The light-emitting apparatus as set forth in claim 1, whereinthe substrate contains heat-radiating vias, made of metal, which arejoined to the light-reflecting layer, the external connection terminals,or both.
 14. The light-emitting apparatus as set forth in claim 13,wherein the heat-radiating vias extend in a direction perpendicular to asurface of the substrate.
 15. The light-emitting apparatus as set forthin claim 13, wherein the heat-radiating vias are made of silver or asilver alloy composed mainly of silver.
 16. The light-emitting apparatusas set forth in claim 1, wherein the at least one semiconductor deviceis placed on the covering layer via an adhesive resin.
 17. Thelight-emitting apparatus as set forth in claim 1, wherein the sealingresin contains a luminescent material.
 18. The light-emitting apparatusas set forth in claim 1, wherein the sealing resin is constituted by aluminescent material-containing resin section containing a luminescentmaterial and a transparent resin section provided so as to cover theluminescent material-containing resin section.
 19. The light-emittingapparatus as set forth in claim 18, wherein the luminescentmaterial-containing resin section and the transparent resin section bothhave domed contours.
 20. The light-emitting apparatus as set forth inclaim 1, wherein the sealing resin has a domed contour.
 21. Alight-emitting apparatus comprising: a light-emitting diode chip; apackage, including a chip-mounting portion where the light-emittingdiode chip is die-bonded and a silver reflecting layer which reflectslight emitted by the light-emitting diode chip and is provided below thelight-emitting diode chip; a sealing resin which covers thelight-emitting diode chip, and external connection terminals; whereinthe silver reflecting layer is covered with a glass layer, thelight-emitting diode chip has a top surface and a bottom surface and isprovided on the glass layer so that the bottom surface faces the glasslayer, and the glass layer covers the entire bottom surface of thelight-emitting diode chip, the silver reflecting layer is not connectedto any of the external connection terminals, the glass layer covers aside surface of the silver reflecting layer, and the light-emittingapparatus comprises a diode chips and the silver reflecting layer is asingle continuous layer that covers bottom surfaces of all of thelight-emitting diode chips.
 22. The light-emitting apparatus as setforth in claim 21, wherein the sealing resin is made of dimethylsilicone or methyl rubber.
 23. The light-emitting apparatus as set forthin claim 21, wherein the sealing resin has a luminescent materialdispersed therein for absorbing at least a portion of primary lightemitted by the light-emitting diode chip and converting the primarylight into secondary light having a longer wavelength than the primarylight.
 24. The light-emitting apparatus as set forth in claim 21,wherein the silver reflecting layer is provided on a periphery of anexit face of the light-emitting apparatus.
 25. The light-emittingapparatus as set forth in claim 21, wherein the chip-mounting portion isprovided with a recessed area whose bottom surface is provided with anelectrode pad.
 26. A light-emitting apparatus comprising: a ceramicsubstrate; external terminals provided on said ceramic substrate, saidexternal terminals being exposed; a metal radiator located in saidceramic substrate; a light-reflecting layer provided on said metalradiator and electrically independent of said external terminals, saidlight-reflecting layer having a thickness smaller than a thickness ofsaid metal radiator, an underside of said light-reflecting layer havinga partial area connected to a top surface of said metal radiator; an LEDchip electrically connected to said external terminals and provided on atop surface of said light-reflecting layer with an insulatortherebetween, wherein the insulator covers the top surface of saidlight-reflecting layer and a side surface of said light-reflectinglayer, and transmits light emitted by said LED chip and reflected bysaid light-reflecting layer; and a sealing resin sealing said LED chip.27. The light-emitting apparatus of claim 26, wherein said externalterminals are provided on an underside of said ceramic substrate. 28.The light-emitting apparatus of claim 27, wherein said sealing resincomprises silicone resin.
 29. The light-emitting apparatus of claim 27,wherein said metal radiator comprises silver.
 30. The light-emittingapparatus of claim 27, wherein said light-reflecting layer comprisessilver.
 31. The light-emitting apparatus of claim 27, wherein saidsealing resin has a domed contour.
 32. A light-emitting apparatuscomprising: a ceramic circuit board comprising a ceramic substrate,first and second external terminals provided on an underside of saidceramic circuit board and being exposed, a light-reflecting layerprovided on the ceramic substrate and electrically independent of thefirst and second external terminals, an insulator covering the topsurface of the light-reflecting layer and a side surface of saidlight-reflecting layer, and transmitting light reflected by thelight-reflecting layer, and positive and negative electrodesrespectively connected electrically to said first and second externalterminals, an underside of each of the positive and negative electrodesbeing located on a same level as an underside of the light-reflectinglayer; an LED chip provided on a top surface of said ceramic circuitboard and located above the light-reflecting layer, the insulator beingprovided between the LED chip and the light-reflecting layer, said LEDchip being electrically connected to the first and second externalterminals via the positive and negative electrodes; and a sealing resinsealing said LED chip.
 33. The light-emitting apparatus of claim 32,wherein said sealing resin comprises silicone resin.
 34. Thelight-emitting apparatus of claim 32, wherein said light-reflectinglayer comprises silver.